Fig 1.
Different strategies used for the isolation of free-living diazotrophs from an Amazon forest soil. (A) Strategy A, direct plating on solid N-free medium incubated inside a hypoxic chamber (2% O2); (B) strategy B, inoculation into semisolid N-free medium with incubation in air for a week, followed by serial dilution and plating on solid N-free medium and incubation inside a hypoxic chamber 2% O2; (C) strategy C, inoculation into semisolid N2-free medium with incubation in air with three subsequent transfers in the same semisolid medium before plating on solid medium amended with NH4Cl. The boxed area represents the 2% O2 condition in the hypoxic chamber. The total number of isolates (n) obtained with each method is provided.